The present invention relates to pipeline air release vent valves and, in particular, it concerns a pipeline air release vent valve having a bi-water-level two stage delayed air vent action.
It is known to provide pipelines with automatic air release valves designed to release entrapped pockets of air usually accumulated at high points along the pipeline. These air release valves are designed to release the entrapped pockets of air while the pipeline is operational and pressurized.
Automatic air release valves in common use today comprises a valve body with a relatively small diameter venting orifice mounted on the top cover of the air release valve. A direct action float with a resilient seal mounted on its top seals the venting orifice as the float rises with the water level within the valve body. The float drops and opens the venting orifice when the water level within the valve body recedes; thereby resuming the operation of releasing the entrapped air within the pipeline.
It will be understood that the rise of the water level within the valve body after the float has sealed the vent orifice creates a situation in which the pressure inside the valve body is higher than the ambient air pressure. Therefore, the direct action float must have a weigh suitable to overcome the pressured differential and open the vent orifice upon the recess of water within the valve body.
Consequently, a float with such significant weigh has relatively low buoyancy and rides low in the water. This brings the water level close to the float's top seal. As a result, as the water level in the valve body rises, the water itself comes in close proximity of the vent orifice, causing a mist of water to spray out of the orifice as it is closing, thereby wetting the outer surface of the air release valve and the surrounding environment. A similar situation occurs when the valve opens. As the valve opens to allow air to enter the pipeline, water near the orifice may splashout.
It should be noted that some automatic air release valves employ a float and lever mechanism to over come this problem, but these valves suffer from utilizing hinged and/or rotating parts that may stick or otherwise become inoperable over time.
There is, therefore, a need for an air release vent valve having a bi-water-level two stage delayed air vent action that distances the air venting orifice from the surface of the water with in the valve body, thereby preventing water mist form spraying out.